Electrically regenerable desalting apparatus

Abstract

Electrically regenerable desalting apparatus having the desalting compartment packed with ion exchangers produced by utilizing radiation-initiated graft polymerization, in which said ion exchangers are nonwoven fabrics in the form of a fiber assembly and a cation exchanger and an anion exchanger are disposed in a face-to-face relationship, with a porous material being interposed between the two ion exchangers. Having the ability to reject ions from liquids, the apparatus is particularly suited to the production of pure water in the electrical power generating industries (including the nuclear industry), electronic industry and the pharmaceuticals manufacturing industry, as well as to the desalting of thick fluids encountered in food and chemical manufacturing processes.

What is claimed is: 
     
       1. An electrically regenerable desalting apparatus having a cation- and an anion-exchange nonwoven fabric disposed in a face-to-face relationship within a desalting compartment as they are compressed together, with a porous material being interposed for creating turbulent flows, wherein (1) a substrate nonwoven fabric for both types of ion exchangers is composed of composite fibers having a core-sheath structure;   (2) a passageway for feed water in the form of an ion-exchanging mixed bed is formed between the cation-and anion-exchanger nonwoven fabrics which are disposed in a face-to-face relationship with said porous material being interposed; and   (3) said feed water is treated by ion exchange as it makes contact primarily with fibers protruding from the surface of each ion-exchanger nonwoven fabric while flowing through said passageway.   
     
     
       2. An apparatus according to claim 1, wherein said substrate nonwoven fabric is an assembly of core-sheath composite fibers, with the sheath component being a polyolefinic high polymer and the core component being any of the high polymers other than the one used as the sheath component. 
     
     
       3. An apparatus according to claim 2, wherein said substrate nonwoven fabric is an assembly of core-sheath composite fibers, with the sheath component being polyolefin and the core component being polypropylene. 
     
     
       4. An apparatus according to claims 1 wherein said substrate nonwoven fabric is produced by thermal fusion. 
     
     
       5. An apparatus according to claims 4 wherein the core-sheath composite fibers used in said substrate nonwoven fabric have a concentric core-sheath arrangement. 
     
     
       6. An apparatus according to claim 5, wherein the core-sheath composite fibers used in said substrate nonwoven fabric have a concentric core-sheath arrangement. 
     
     
       7. An apparatus according claim 5, wherein ion-exchange groups are introduced into said substrate nonwoven fabric by utilizing radiation-initiated graft polymerization. 
     
     
       8. An apparatus according to claim 7, wherein said ion-exchange groups have at least a sulfonic acid group as a cation-exchange group and at least a quaternary ammonium salt as an anion-exchange group. 
     
     
       9. An apparatus according to claims 7, wherein said ion-exchange groups have an ion-exchange capacity in the range from 0.5 meq/g to 3 meq/g in terms of a capacity for decomposing neutral salts. 
     
     
       10. An apparatus according to 1, wherein the polymerizable monomer to be grafted onto said substrate nonwoven fabric either has ion-exchange groups or can be converted to ion-exchange groups. 
     
     
       11. An apparatus according to claim 10, wherein said ion-exchange groups have at least a sulfonic acid group as a cation-exchange group and at least a quaternary ammonium salt as an anion-exchange group. 
     
     
       12. An apparatus according to claim 11, wherein said ion-exchange groups have an ion-exchange capacity in range from 0.5 meq/g to 3 meq/g in terms of a capacity for decomposing neutral salts. 
     
     
       13. An apparatus according to claim 1, wherein the desalting compartment has a thickness of 3-5 mm. 
     
     
       14. An apparatus according to claims 1, wherein said substrate nonwoven fabric has a thickness of 0.1-1.0 mm. 
     
     
       15. An apparatus according to claims 1 wherein said substrate nonwoven fabric has an areal density of 10-100 g/m 2 . 
     
     
       16. An apparatus according to claims 1, wherein said substrate nonwoven fabric has a porosity of 50-98%. 
     
     
       17. An apparatus according to claims 1, wherein the fibers composing said substrate nonwoven fabric have diameters of 10-70 μm. 
     
     
       18. An apparatus according to claim 1, wherein the porous material interposed between said two ion-exchange nonwoven fabrics is a synthetic resin net having a thickness of 0.3-1.5 mm. 
     
     
       19. An apparatus according to claim 1, wherein said desalting compartment has a thickness of 3-5 mm, said substrate nonwoven fabric has a thickness of 0.1-1.0 mm, an areal density of 10-100 g/m 2  and a porosity of 50-98%, the fibers composing said substrate nonwoven fabric have diameters of 10-70 μm, and the porous material interposed between said two ion-exchanger nonwoven fabrics is a synthetic resin net having a thickness of 0.3-1.5 mm, whereby fibers in each of said two ion-exchangers nonwoven fabrics are allowed to protrude toward said passageway. 
     
     
       20. An apparatus according to claim 1, wherein ion-exchange groups are introduced into said substrate nonwoven fabric by utilizing radiation-initiated graft polymerization.